The measurement of panels of biomarkers has promise for increased diagnostic value in cancer detection and treatment compared to the measurement of single markers. Furthermore, to increase their effectiveness in the early detection of cancer, where the markers may have very low concentrations, or where small changes in concentration may be significant, assays with higher sensitivity are needed. The objective of this proposal is to develop a nanotechnology-based biosensor to simultaneously measure the concentrations of multiple tumor markers (TMs) with high sensitivity. The system consists of an electrochemical array for mulitanalyte measurement, nanoparticle assay labels to provide significant assay signal amplification, and a portable device for reading and quantifying the assays.